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Breaking the Buck: Loss of Constant NAV in Money Market Funds

An in-depth examination of what it means when a money market fund's NAV falls below $1, causing significant implications for investors and the financial market.

“Breaking the buck” refers to an event in which the net asset value (NAV) of a money market fund falls below the usual $1 per share. This deviation signifies that the fund’s assets have decreased in value to a point where they no longer maintain the stable $1 NAV, typically due to severe losses or insufficient investment income to cover operating expenses.

Origins and Historical Context

Money market funds are typically considered low-risk investments, often utilized by individuals and institutions for their perceived safety and liquidity. Historically, these funds aim to maintain a stable NAV of $1 to provide stability and predictability. The first notable instance of “breaking the buck” occurred in 2008 when the Reserve Primary Fund’s NAV fell to $0.97 amid the financial crisis, leading to widespread panic and a run on money market funds.

Severe Losses

A substantial decline in the value of the fund’s investments, such as default on securities or significant market downturns, can cause the NAV to drop:

$$ \text{NAV} = \frac{\text{Total Assets - Liabilities}}{\text{Total Shares Outstanding}} $$

Income Below Operating Expenses

If the return on the fund’s investments is insufficient to cover its operating expenses, the NAV may also decline:

$$ \text{Net Investment Income} = \text{Interest Income} - \text{Operating Expenses} $$

Types of Money Market Funds Susceptible to Breaking the Buck

  • Prime Money Market Funds: Invest in corporate debt, carrying higher credit risk.
  • Government Money Market Funds: Hold government securities, typically considered safer but not immune to extreme market conditions.
  • Tax-Exempt Money Market Funds: Invest in municipal bonds, subject to different risks based on local government solvency.

Investor Confidence

A drop below $1 can erode investor confidence, prompting redemptions and potentially exacerbating fund instability.

Regulatory Response

Post-2008, regulatory changes such as the SEC’s Rule 2a-7 have been implemented to increase transparency and reduce the risk of breaking the buck.

Reserve Primary Fund (2008)

The Reserve Primary Fund’s NAV fell to $0.97 on September 16, 2008, due to losses on Lehman Brothers’ commercial paper, sparking a large exodus from money markets.

  • Net Asset Value (NAV): The per-share value of an investment fund.
  • Run on the Fund: When numerous investors withdraw their funds simultaneously, often precipitated by fear of breaking the buck.

FAQs

What happens to investors when a money market fund breaks the buck?

Investors may experience losses on their investments and reduced access to liquid funds.

Are money market funds still considered safe?

Post-2008 reforms have strengthened safeguards, but money market funds still carry some risk.
Revised on Monday, May 18, 2026